As is known, the electric light has a strong impact on the circadian rhythm; in particular, artificial light hitting the retina between dusk and dawn inhibits the action of neurons which promote sleep, activates the production of orexin in the hypothalamus, and suppresses the nocturnal release of melatonin, which phenomena result in reduction of drowsiness, increased alertness and interference with sleep.
Studies conducted by Czeisler (“Casting light on sleep deficiency” Nature, 497, S13, 2013) show that 30% of American office workers and 44% of night workers complain about sleeping, on average, less than 6 hours a night, while only 3% of the American adult population slept so little in 1960. Moreover, the article notes that optoelectronic devices with light emitting diodes (LED), such as television, computer screens, laptops, tablets and mobile phones, use a type of white light which is rich in blue light. The ipRGCs (photosensitive ganglion cells), which are found in the eye, are more sensitive to light which is visible at low wavelengths (blue and green), says Czeisler, therefore the exposure to LEDs in night hours generally causes a greater interruption of circadian rhythm, melatonin secretion and sleep compared to night exposure to light from light bulbs.
Further studies, conducted by Masuda and Watanabe (Short Wavelength Light-Induced Retinal Damage in Rats. Jpn J. Ophthalmol., 44:615-61 9, 2000) showed that the light at wavelengths of 350 nm causes damage to photoreceptor cells, while light at wavelengths of 441 nm damages the retinal pigment epithelium. In an article entitled “Evaluation of Blue-Light Hazards from Various Light Sources”, 2002, Progress in lens and Cataract Research, Tsutomu Okuno stresses that an average exposure of 270 seconds a day to the blue light of the LEDs can lead to photochemical retinal damage.
This type of damage to the retina has been studied by Elawady A. Ibrahim (Neuroprotective Effects of Grape Seeds against Photo-Chemical Damage-Induced Retinal Cell Death. Nature and Science 9(11):83-89, 2011): he argues that prolonged exposure to blue light permanently damages the retinal neurons.
Roehlecke et al. (Influence of blue light on photoreceptors in a live retinal explants system. Molecular Vision 17: 876-884, 2011) also reported in vitro studies in which the irradiation of blue light on retinal transplants produces ultra-structural changes involving necrosis of the photoreceptor cells.
Recently, in vitro and in vivo studies have shown that the irradiation of blue light at 470 nm affects the central nervous system, can cause the complete reset of the circadian rhythm (Jones—Manipulating circadian clock neuron firing rate resets molecular circadian rhythms and behavior—Nature Neuroscience, Advance Online Publication).
Although physical protections against blue light (such as spectacles and screens for monitors) are available on the market, these solutions are usually bulky or expensive.
In addition, although contact lenses are available for this purpose, the latter involve the same side effects (e.g. hyperemia, eye infections, corneal ulcers) as conventional lenses.
It is also known that carotenoids are a class of organic compounds present in plants and other photosynthetic organisms. They are usually divided into two classes, depending on the presence or absence of oxygen atoms within the molecule: the first is that of xanthophylls, while the last comprises carotenes. The color of these molecules ranges from light yellow to bright red depending on the type of wavelengths absorbed and reflected.
It has been widely documented that a diet based on carotenoids protects from damage caused by free radicals since these compounds, rich in double PI bonds, can oxidize and eliminate noxious species from the body.
The oxidative degradation products, called apocarotenoids, are in many cases molecules with further beneficial effects, as in the case of vitamin A (retinol, retinoic acid, retinal), bixin and crocetin.
Apocarotenoids are able to absorb blue light, as in the case of bixin (Food Chemistry 141; 4: 3906-3912, 2013) and crocin, the ester of crocetin (Invest. Ophthalmol. Vis. Sci. 47: 3156-3163, 2006).
To date, there are no chemical compounds on the market capable of ensuring an effective protection of eyes from blue light; WO 2004/063363 describes hyaluronic acid retinoic esters as useful products for the differentiation of totipotent stem cells. On the other hand, it is also known that eye drops are not optimal methods for the administration of active ingredients, since they have low bioavailability and are thus subject to a low therapeutic response, mainly due to the presence, in the eye, of drainage systems: for this reason, products of this type require multiple applications in order to achieve the desired therapeutic effect.
The interest in developing compounds which are able to protect the eyes from damage caused by blue light radiation is apparent from the above.